In recent years, as an earphone for a portable audio reproducing device, an inner-ear-type earphone, a neckband-type earphone, and the like have been becoming widely used. Of the above-mentioned earphones, the neckband-type earphone includes relatively small headphones and is excellent in design unlike a headphone device in which a band section for coupling driver units together is held over a head.
In the neckband-type earphone, driver units of earphones are coupled by a band section. The band section has a U-shape, and a band of the band section is arranged in a vicinity of a back of a head of a wearer when the wearer wears the neckband-type earphone. The neckband-type earphone as described above is disclosed (for example, see Patent Literatures 1 and 2).
Further, as another related-art earphone, there is known a neckband-type earphone in which a reproducing unit for reproducing an audio signal is provided on a back side of a neckband (for example, see Patent Literature 3). In such a related-art neckband-type earphone, the reproducing unit itself is provided in the neckband-type earphone, and hence it is not necessary to connect the reproducing device and the neckband-type earphone through a cable. Accordingly, for example, when a user walks during commuting to work or plays sports such as jogging, the user does not need to care about the cable and can concentrate on playing sports.
Further, in recent years, a device for transmitting the audio signal through a radio wave has been known as means for transmitting the audio signal from the reproducing device to the earphone, instead of transmitting the audio signal from the reproducing device to the earphone through the cable as in the related art. In a case of the above-mentioned device for transmitting the audio signal through the radio wave, the reproducing device includes a transmitting unit for outputting the audio signal through the radio wave, whereas the earphone includes a receiving unit for receiving the audio signal. Thus, through the radio wave, the neckband-type earphone receives the audio signal reproduced by the reproducing device.